Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

533
FXUS63 KLOT 112325
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
525 PM CST Sun Jan 11 2026

.KEY MESSAGES...

- Up and then down temperatures are expected this week with
  multiple opportunities for precipitation.

- The main concern from a winter weather perspective is
  Wednesday into Thursday, with wind-whipped snow showers
  during the day Wednesday possibly followed by accumulating
  lake effect snow Wednesday night into Thursday morning.

&&

.DISCUSSION...
Issued at 132 PM CST Sun Jan 11 2026

Through Monday:

No significant weather is expected in the short term. The main
question relates to sky cover trends the rest of the afternoon
and evening. A lowering subsidence inversion continues to chew
away at the top layer of cloud cover, with regional satellite
and webcams indicating the stratus deck overhead is extremely
thin. Have recently seen quite a few holes and clearing
developing across parts of NE Illinois and E Wisconsin. However,
with the mean cloud-bearing flow backing to the southwest,
additional cloud cover closer to our west should slosh eastward
through the rest of the afternoon. There`s a nicely-defined
back edge to cloud cover though, and tracking this out suggests
things should begin to clear out quickly near I-39 early this
evening and then prior to midnight across the rest of the area.

Overnight, a stout shortwave currently pushing through southern
Manitoba will pass to our north. Other than spreading some
additional high cloud cover and increasingly southwesterly
breezes, no significant impacts are expected in our area.
Temperatures on Monday should warm into the low to locally mid
40s.

Carlaw


Monday Night through Sunday:

As has been advertised, anomalously strong mid-upper ridging
will establish near the Pacific Coast through next week, with
downstream troughing carved out across much of eastern North
America. This represents the positive phase of the Pacific North
American (PNA) teleconnection pattern, typified by a
predominantly northwesterly flow pattern into the Great Lakes
region. A stretch of solidly above normal temps to start the
workweek will peak on Tuesday, followed by a return to more
seasonable readings for mid-January through the rest of the week
(near to below normal temperatures). The deep northwest flow
pattern will be unfavorable for any moisture-laden synoptic
systems, so overall precip amounts for the week will tend to
skew towards the lighter end of the spectrum. This certainly
does not preclude any impactful winter weather, however, with a
persistent signal for accumulating lake effect snow somewhere
downwind of southern Lake Michigan Wednesday PM into Thursday.

Forecast low temperatures Monday night are near to slightly
above the normal high temperatures for this time of year (in
the lower to mid 30s). This will provide a mild starting point
for highs in the upper 40s to around 50F on Tuesday. The next
clipper-type wave tracking into the northern Great Lakes will
induce breezy west-southwest winds gusting to 25-30 mph.
Isolated to widely scattered showers or sprinkles will be
possible (20-30% PoPs) from the mid-level overcast out ahead of
the system cold front, which will sweep across the area by
Tuesday evening.

Most of Tuesday night will be quiet and breezy with
temperatures still above normal. This will abruptly change by
Wednesday morning as a robust PV anomaly dives southward across
the area in tandem with a secondary cold front passage packing
much stronger cold air advection. As winds shift to north-
northwesterly with gusts up to 30-40 mph, strong large scale
forcing will result in quickly blossoming snow showers on
Wednesday.

While there`s still some uncertainty in the westward extent of
sufficient moisture through the DGZ, run-to-run continuity
across the suite of global ensemble systems remains good on the
whole and supports the latest NBM initialization`s 30-80% PoPs
across our forecast area on Wednesday (highest PoPs in northeast
Illinois and northwest Indiana and lowest PoPs towards northwest
and central Illinois). Depending on how this setup evolves from
a convergence perspective, very steep low-level lapse rates
could yield embedded snow squalls. While surface temperatures
and mild antecedent ground conditions to start the day may
initially limit accumulation/impact potential, temperatures
falling into the 20s in the afternoon could paint a different
story heading into the evening commute.

The main change noted from previous model cycles is slower and
stronger with the PV anomaly/very cold closed 500 mb low diving
south across the region. This entails cyclonic flow lingering
into Wednesday night, important to most effectively tap into
good lake-induced thermodynamics (vs. a more subsident regime
serving as a limiting factor). It`s much too early to be
confident in the details for this period. However, from a
pattern recognition perspective, accumulating lake effect snow
is appearing more likely downwind of southern Lake Michigan (and
possibly well downwind at that) due to deep near-unidirectional
northerly flow and the synoptic assist from the departing PV
anomaly. Could see some hybrid aspects as seen with the November
9-10 lake effect snow event per some recent guidance member
depictions. The forecast northerly boundary layer flow continues
to warrant boosting PoPs Wednesday night into the 50-60% range
near/east of I-57 in Illinois into northwest Indiana.

Any break following the probable lake effect snow showers may
be short-lived, with signs pointing toward an additional clipper
system or two affecting the region sometime in the Thursday
night-Saturday timeframe. Some guidance members continue to
suggest that the clipper short-wave could temporarily become a
cut-off low into the start of the weekend, which greatly
increases uncertainty in how it will evolve. Maintained broad-
brushed chance PoPs peaking in the 30-50% range Thursday night-
Friday night given approximately that much ensemble member
support. Nonetheless, the spectrum of plausible outcomes here is
quite large, from on-and-off light snow/snow showers to little
or no snow. Expect generally below normal temperatures to close
out the week and into next weekend.

Castro/Ogorek

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 525 PM CST Sun Jan 11 2026

- MVFR stratus ending from west to east this evening

- Gusty WSW winds develop overnight with gusts around 25 kt

The back edge of the MVFR stratus layer is approaching the area
early this evening with a return to VFR expected from west to
east over the next 1-4 hours. Latest guidance paired with
satellite trends suggests this may arrive a bit slower and opted
to delay the timing by an hour. VFR conditions then prevail
through the remainder of the TAF period with varying coverage of
high clouds.

West southwest winds are forecast through the period. They may
become increasingly gusty late this evening and overnight.
Confidence in just how strong the gusts end up remains on the lower
side and will be dependent upon whether some decoupling occurs
(lower gusts) or if the low-levels can remain more mixed and
tap into the increasing low-level flow aloft (higher gusts).
With that said, opted to nudge up gusts into the mid-20 kt range
with this update. A few gusts to near 30 kt can`t be ruled out.
The more frequent gusts then ease during the morning on Monday
with winds around 10-12 kt and occasional gusts nearing 20kt at
times before easing toward sunset.

Petr

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 9 PM this evening to 9 AM CST Monday
     for Winthrop Harbor IL to Gary IN.

     Small Craft Advisory until noon CST Monday for Gary to Burns
     Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

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